Assessment of DFT for Computing Sum Frequency Generation Spectra of an Epoxydiol and a Deuterated Isotopologue at Fused Silica/Vapor Interfaces

Abstract

We assess the capabilities of eight popular density functional theory (DFT) functionals, in combination with several basis sets, as applied to calculations of vibrational sum frequency generation (SFG) spectra of the atmospherically relevant isoprene oxidation product trans-β-isoprene epoxydiol (IEPOX) and one of its deuterated isotopologues at the fused silica/vapor interface. We use sum of squared differences (SSD) and total absolute error (TAE) calculations to estimate the performance of each functional/basis set combination in producing SFG spectra that match experimentally obtained spectra from trans-β-IEPOX and one of its isotopologues. Our joined SSD/TAE analysis shows that while the twist angle of the methyl C3v symmetry axis of trans-β-IEPOX relative to the surface is sensitive to the choice of DFT functional, the calculated tilt angle relative to the surface normal is largely independent of the functional and basis set. Moreover, we report that hybrid functionals such as B3LYP, ωB97X-D, PBE0, and B97-1 in combination with a modest basis set, such as 6-311G(d,p), provides good agreement with experimental data and much better performance than pure functionals such as PBE and BP86. However, improving the quality of the basis set only improves agreement with experimental data for calculations based on pure functionals. A conformational analysis, based on comparisons of calculated and experimental SFG spectra, suggests that trans-β-IEPOX points all of its oxygen atoms toward the silica/vapor interface.

Trimethylamine-N-oxide: its hydration structure, surface activity, and biological function, viewed by vibrational spectroscopy and molecular dynamics simulations

“…39 Moreover, the harmonic calculations cannot address the contribution of the Fermi resonance, because they do not take into account any vibrational mode couplings. To address the anharmonic correction and the Fermi resonance, the vibrational Hamiltonian approach, 40,41 vibrational self-consistent field (VSCF) approach, [42][43][44] or perturbative approach 45 should be employed. The vibrational Hamiltonian approach is more computationally inexpensive, but it is more empirical than the VSCF-based approach.…”

Atmospheric β-Caryophyllene-Derived Ozonolysis Products at Interfaces

“…Density functional theory (DFT) calculations were employed to aid in spectral interpretation. Similar to our previous work, , geometries for a number of different conformers of each oxidation product were optimized by using B3LYP − /6-311G­(d,p) via the Gaussian09 software package located at Yale University . Upon optimization, the harmonic and anharmonic frequencies were calculated in addition to the dipole and polarizability derivatives with respect to each normal mode.…”

Proton transfer in the benzimidazolone and benzimidazolthione tautomerism process catalyzed by polar protic solvents

“…The calculated harmonic vibrational wavenumbers were scaled with 0.9665 for CAM-B3LYP/6-311G(d,p) level. 50 We have also performed calculations in three different solvents (ε = 2.3, benzene C 6 H 6 ); (ε = 32.63, methanol CH 3 OH); and (ε = 78.39, water H 2 O) using the polarizable continuum model (PCM). 51,52 The thermodynamic quantities have been calculated at 298.15 K for all the optimized geometries.…”